Zimbabwe has been elected to head the UN's commission on Sustainable Development (CSD) despite strong objections from Western diplomats.
Mr Chidyausiku says the row is a storm in a teacup
They had said Zimbabwe was unsuitable because of its human rights record and economic problems. It is suffering food shortages and rampant inflation.
But Zimbabwe has dismissed such criticism, calling it an insult.
The country was chosen by other African nations. The CSD post rotates every year between the world's regions.
Zimbabwe was elected to lead the commission by a 26-21 secret ballot among CSD members at the UN headquarters in New York. There were also three abstentions.
There was a brief round of applause as the result was announced.
Developing nations appear to have voted for Zimbabwe, the BBC's Laura Trevelyan in New York says.
They respected the decision of the African group to nominate the country for the post in the first place, and they have shown they cannot be pushed around, our correspondent says.
Zimbabwe's Environment Minister Francis Nheme will now become chairman of the CSD.
Mr Nheme is the subject of European Union travel ban because he is a member of President Robert Mugabe's government.
That means he cannot travel to the EU to meet ministers on commission business.
Zimbabwe's Ambassador to the UN, Boniface Chidyausiku, said before the vote that his country was entitled to hold the chairmanship.
"It's our right. We're members of the United Nations and we're members of CSD, and the Africa group did make a decision and endorsed Zimbabwe," he told the BBC's Network Africa programme.
"They're making a storm out of a teacup."
He said the real objection came down to Britain's criticism of Zimbabwe's controversial land reform programme.
Zimbabwe was once a prosperous food exporter, but production has plummeted since land reforms in 2000 that saw thousands of white-owned farms seized.
"We see it as a translation of a bilateral quarrel between London and Harare on the land reform programme," Mr Chidyausiku said.
He said the European countries should respect the decision of the African block.
"When they tell the African group to change, it's an insult to our intelligence - that we Africans can't think," he said.
Meanwhile, Mozambique has threatened to cut electricity to its neighbour for failing to pay its debts.
Mozambique's Cahora Bassa dam supplies Zimbabwe with 500 megawatts of power.
The BBC's Jose Tembe in Maputo says Zimbabwe has accumulated debt to the tune of $9m.
A spokesman for Mozambique's electricity firm EDM said the government acknowledged Zimbabwe's current economic crisis but said that debt is debt and must be paid.
On Wednesday, it was announced that households in Zimbabwe were to be limited to four hours' electricity a day, between 1700 and 2100 local time.